In mobile communication networks, e.g., according to the technical specifications of the Third Generation Partnership Project (3GPP), concepts have been introduced according to which several channels using different carriers can be bundled in a single radio link. These concepts are also referred to as carrier aggregation. More generally, carrier aggregation can be defined as defining a constellation of two or more component carriers to be used for signal transmission. Examples of carrier aggregation are contiguous carrier aggregation, in which the constellation consists of two or more adjacent component carriers, non contiguous intra-band carrier aggregation, in which the constellation consists of two or more non-adjacent component carriers from the same frequency band or spectrum, and inter-band carrier aggregation or spectrum aggregation, in which the constellation consists of two or more component carriers from at least two different frequency bands or spectra. In the following, the term spectrum will be used to refer to a frequency band, i.e., a contiguous frequency range, or to a group of frequency bands which do not need to be contiguous among each other.
Typically carrier aggregation in a mobile communication network is done with component carriers from a spectrum allocated to the radio access technology of the mobile communication network, e.g., a licensed spectrum. However, the number of such spectra and also the number of component carriers in such spectra is limited. A way of increasing the number of component carriers available for carrier aggregation is so-called secondary or opportunistic use of a spectrum that is primarily used by another technology, e.g., a television, a satellite or a radar technology. In this way, a significant increase of transmission capacity can be obtained. However, it also needs to be taken into account that the secondary use of a spectrum does not interfere with a primary user of this spectrum. For example, regulatory rules for secondary spectrum access of television channels have been defined by the United States Federal Communications Commission (US FCC).
Typically, a secondary spectrum may be used opportunistically by the mobile communication network while not interfering with a primary user of the secondary spectrum, e.g., while primary users are inactive. However, a primary user may become active at some time, which means that component carriers in the secondary spectrum may need to be vacated very quickly, e.g., within some milliseconds.
Accordingly, there is a need for techniques which allow for efficiently controlling aggregation of component carriers from different spectra.